Plot
Kaiju.They are the protectors of the earth,and have been here for millions of years.However due to unknown reasons,they are coming out of their dormant states.In an act of defense,humans made mechanized version of these creature and of their own design.However, the Kaiju have evolve in more ways then one.With most gain a unique powers.However that wasn't the reason the creature woke up,as other kaiju,not known in legends,are coming to destroy the planet.Either human find a way to work with them,or the Earth is doomed.

Roles

Titans
Creatures from long ago.Each have an effect on the Planet,whenever it's an positive or negative.Clearly they been on the earth longer than we have,and the exact reason on why they's becoming active now is currently unknown.But it seems each and every one of them has a goal in mind.A goal that they agreed on.Their sheer size,makes it impossible for us to harm them.Also they seem to use Radiation as a food source.Meaning they will attack major cities if they need to feed.They also have a number of abilities.

Humans
Creautres that live today.They build cities,and small town.Compared to the past times,they have evolved quick when the Kaiju expected.Quick enough to make Food for the Titans.But they are intelligent.Able to make their own Kaiju,their own monsters.Weapons strong enough to kill.Able to analyze a Titan's weak spot.They could also use the blood of titans to make their ow hybrids made to fight

Aliens
We do not know where they come from,but legends has it that they made creatures strong enough to kill Titans.But they are worse.They can make them in a time span of two days,which means that the titans evolved not only to survive,but to fight the threat on their world.Not much is known about them expect that.

Jk... let's see here, it can be like.. a couple of feet smaller than Godzilla, armed with a twin-barreled automatic shotgun with shells bigger than a human. And I guess... a scatter rocket thingy? Maybe some type of protruding scythe I'll name it the Reaper mech. I guess it will be a bulky fellow, covered in armor, well guarded in the cockpit